The power of "asking for it," they say, can result in everyday lower prices, as well as a significant increase in lifetime earnings. In fact, Babcock says that once when she was out shopping for jewelry, she asked for a lower price and ended up making the purchase at a 20 percent discount.

Roxana Popescu, creator of The Daily Asker website, where she documents her negotiating success, suggests always negotiating in situations where you can offer something in return, or at least not add to a company's costs.

"Hotels are often willing to cut rates if they're not at capacity or upgrade you if it's no cost to them. For example, if they have empty rooms when you check in ... For restaurants, think volume. When you're spending more than the average bill -- say, takeout for a birthday party or reserving a room for a private party -- you have a lot of negotiating power. Either ask for a break on the price or see if they'll throw in some extras, like a birthday cake," she says. In exchange, she suggests, consider what you can offer, such as loyalty, gratitude, the promise of repeat business, or a mention of their brand to your 500 Twitter followers.

The same strategy works in customer-service snafus. Each year, millions of consumers are bombarded with payment problems, from improperly denied health insurance claims to underpayment of Social Security funds. At the Social Security Administration, the inspector general found that between 1990 and 2006, more than 90,000 Social Security recipients were underpaid a total of $120.4 million -- some by as much as $25,000.

Those startling numbers show the importance of checking up on how companies and agencies determine what you owe them and what they owe you. Sometimes they make mistakes, and being vigilant is the only way to make sure you get your money. But many people never see their cash again because they don't notice the problem, don't have time to call, or worst of all, don't feel they have the right to complain.

According to Jon Yates, the official problem solver at the Chicago Tribune and author of the new book
What's Your Problem?: Cut Through Red Tape, Challenge the System, and Get Your Money Back,
we can often win the fights we have with companies as long as we're persistent -- and willing to take our business elsewhere, if necessary. "If you're not making progress, I always suggest hanging up and calling back. Almost always, you will get another customer service rep -- hopefully one who is more understanding and willing to help," he says.

In fact, Yates says the most common mistake people make is giving up too soon. "I talk to people who get frustrated after one or two fruitless calls. Persistence pays off -- and so does being a pain the rear ... If you have the truth on your side and a willingness to battle, you can almost always win," he says.

Women are also more likely to overpay because they tend to be less comfortable with the idea of lodging complaints, says Babcock. She says negotiating for a fair price or complaining about a charge need not mean conflict, which is what scares some people off. Instead, think: "We have an issue ... and we can work to fix the problem together," she says. If a company has made an error, it will want to find a solution and ensure the customer is satisfied, she adds.

According to a survey by Bob Sullivan, author of
Gotcha Capitalism: How Hidden Fees Rip You Off Every Day-and What You Can Do About It,
those of us who make our voices heard have a decent chance of getting the desired results: Complaints to credit card companies and airlines had a success rate of more than 60 percent. (If you're calling to complain to your cable provider, however, you may want to first hone your debating skills: Only 20 percent of those consumers got the response they were looking for.)

Despite their sometimes impenetrable automated phone lines, companies are not the omniscient, technologically advanced entities they often present themselves to be. They aren't even that smart sometimes. But sometimes, making the call is worth the inconvenience and stress. You could find yourself hundreds of dollars richer.